Sitting for longer periods is bad for your your health as well as your posture. These two have been medically proven. Options to longer sitting durations are eitehr to take a break every 45 or so minute and take a walk / strech, or get yourself a desk with adjustable height mechanism, so you can work standing up.

Good standing desks are sturdy, reliable, affordable and come with generous warranties. They also have adjustable-height mechanisms.

There are also DIY standing desks. Just search online..For example, Colin Nederkoorn has devised Standesk 2200, an IKEA modification, which has become very popular. However, DIY standing desks may not be adjustible.

Did you know" Standing for longer duration also improves your standing, making you feel tall?

The best standing desk: Jarvis Bamboo (seven year warranty)

The best affordable standing desk: Kangaroo Pro Junior (helps you convert your existing desk into an adjustable desk, switch easily between sitting and standing)